If the dirt is too tough, just pour some undiluted shampoo on it
Try washing your car under shade always.
Day-in and day-out, your car is moving through dusty streets and muddy roads. All this makes the car appear dull. That is why you need 3M Car Wash shampoo. The shampoo works with soft and hard water and its easy rinse foam removes tough dirt and grime, without effecting the paint surface and wax.